This invention relates to biomedical devices. In particular, the invention provides biomedical devices on the surfaces of which stable, hydrophilic, amide-containing coatings are formed.
Devices for use in and on the human body are well known. The chemical composition of the surfaces of such devices plays a pivotal role in dictating the overall efficacy of the devices. For example, many devices, including catheters, stents, lenses, and implants require biologically non-fouling surfaces, meaning that proteins, lipids, and cells will not adhere to the surfaces. Lenses also must be wettable by tear fluid in order to ensure wearer comfort. Additionally, providing such devices with an antimicrobial surface is advantageous.
A wide variety of methods have been developed to coat device surfaces to provide them with desired characteristics. However, the need still exists for a simple, efficient process that will provide a stable, hydrophilic coating.
The present invention provides a simple, economical process for producing devices with stable amide group-containing coatings including, without limitation, polyacrylamide coatings. In one embodiment, the invention provides a method for manufacturing biomedical devices comprising, consisting essentially of, and consisting of contacting at least one surface of a biomedical device, the surface comprising, consisting essentially of, and consisting of an effective amount of carboxyl groups with a coating-effective amount of an amine and a coupling effective amount of at least one coupling agent under conditions suitable to produce a stable, amide-containing coating on the surface. In another embodiment, the invention provides biomedical devices comprising, consisting essentially of, and consisting of a biomedical device at least one surface of the device having an amide-containing coating coupled thereto by at least one coupling agent.
By xe2x80x9cbiomedical devicexe2x80x9d is meant any device designed to be used while in or on either or both human tissue or fluid. Examples of such devices include, without limitation, stents, implants, catheters, and ophthalmic lenses. In a preferred embodiment, the biomedical device is an ophthalmic lens including, without limitation, contact or intraocular lenses. More preferably, the device is a contact lens.
It is an unexpected discovery of the invention that devices having carboxyl groups on their surfaces may be contacted with an amine to provide a hydrophilic, amide-containing coating for biomedical devices. It is another unexpected discovery of the invention that a high conversion of carboxyl groups to amide groups is obtained through the process of the invention. More specifically, a conversion of greater than about 80 percent, more preferably greater than about 90 percent, most preferably about 95 percent or greater, of the carboxyl groups to amide groups may be obtained. The carboxyl groups must be present in an amount effective to produce the desired number of amide groups when reacted with an amine. This amount is an amount of carboxyl groups per square centimeter of lens surface of about 0.65 to about 65 nMol/cm2, preferably about 1 to about 50, more preferably about 1 to about 10 nMol/cm2 of carboxyl groups.
In the process of the invention, a coating-effective amount of an amine is used, which amount is sufficient to convert the carboxyl groups present to the desired degree. The amine may be used as a part of a solution containing a solvent, such as an alcohol, tetrahydrofuran, or the like, or an aqueous solution. Preferably, an aqueous solution is used. The amount of amine in the solution may be about 5 volume percent, preferably about 1 volume percent, more preferably less than about 1 volume percent. The coatings produced by the process of the invention are stable, meaning that subjecting the coating to autoclaving, washing with a cleaning agent, and/or rinsing with a saline solution does not substantially alter the chemical properties of the coating.
A coupling effective amount of the coupling agent is used which amount is sufficient to enable to reaction of the carboxyl groups with the amine. The precise amount of coupling agent used will depend on the surface""s chemistry as well as the amine and coupling agent selected. The amount of coupling agent used generally will be about 0.01 to about 25 weight percent, preferably about 0.1 to about 15, more preferably, about 0.1 to about 10 weight percent of the coating solution, or solvent, coupling agent and optional buffer. Suitable solvents are those capable of solubilizing both the amine and the coupling agent. Preferably, the process is carried out in a water, or aqueous, solution.
The contacting time typically may be about 1 to about 360 minutes, preferably 1 to about 240 minutes. The contacting temperature may be about 0 to about 95, preferably about 5 to about 80xc2x0 C. The contacting, or reacting, of the amine and carboxyl groups may be carried out in any convenient manner.
Amines useful in the invention are any primary or secondary amines, their corresponding acid salts, amine-containing proteins, amine-containing antibiotics, and the like, and combinations thereof Examples of useful amines, proteins, and amine-containing antibiotics include, without limitation., ammonium chloride, glucosamine hydrochloride, dimethylamine hydrochloride, ethanolamine hydrochloride, diethanolamine hydrochloride, polyethylene glycol amines such as hexa(ethyleneglycol)-bis-amine, lactoferrin, lysozyme, albumin, casein, cytochrome C, immunoglobulins, avidin, heparin, polymyxin, and the like, and combinations thereof.
Coupling agents useful in the invention include any coupling agent capable of enabling the reaction of a carboxyl group with an amine group to form an amide. Useful suitable classes of coupling agents include, without limitation, dehydrating agents such as carbodiimides, acid halides of inorganic or organic acids, isocyanides, and the like, and combinations thereof Examples of suitable coupling agents include, without limitation, carbodimides, N,Nxe2x80x2-carbonyldiimidazole, phosphoryl chloride, titanium tetrachloride, sulfuryl chloride fluoride, chlorosulfonyl isocyanate, phosphorus iodide, pyridinium salts of tributyl amine, phenyl dichlorophosphate, polyphosphate ester, chlorosilanes, and the like as well as mixtures of tributyl phosphorus and phenyl isocyanate, alkyl chloroformates and triethyl amine, 2-chloro-1,3,5-trinitrobenzene and pyridine, methyl sulfuryl chloride and diethyl amine, and triphenylphosphine, carbon tetrachloride and triethyl amine. Preferred coupling agents are carbodiimides. More preferred are 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and dicyclohexyl carbodiimide.
The devices used for purposes of the invention may be made of one or more carboxyl functional hydrophilic polymers. Alternatively, one or more surfaces of a device may be coated with one or more carboxyl functional polymers. Thus, in yet another embodiment, the invention provides a method for manufacturing biomedical devices comprising, consisting essentially of, and consisting of coating at least one surface of a device with one or more carboxyl functional polymers, subsequently contacting the at least one surface with a coating-effective amount of an amine and a coupling effective amount of at least one coupling agent under conditions suitable to produce a stable, amide-containing coating on the surface.
Examples of suitable carboxyl functional hydrophilic polymers include, without limitation, poly(acrylic acid), poly(methacrylic acid), poly(maleic acid), poly(itaconic acid), block or random copolymers of (meth)acrylic acid, acrylic acid, maleic acid, itaconic acid with any reactive vinyl monomer, carboxymethylated polymers, such as carboxymethylcellulose, and the like, and mixtures thereof. Preferably, the carboxyl functional hydrophilic polymer is poly(acrylic acid) or poly(methacrylic acid). More preferably, poly(acrylic acid) is used.
The carboxyl functional polymers may be of any molecular weight. Preferably, the polymers are of a relatively high molecular weight, or about 10,000 to 10,000,000 more preferably about 50,000 to about 4,000,000 g/mole, most preferably about 100,000 to about 1,000,000 g/mole.
Suitable surfaces for coating with a carboxyl functional polymer are any surfaces with hydroxyl groups, amino groups, or mixtures thereof Preferably, the surface is made of a silicone elastomer, silicone-containing macromers including, without limitation, those disclosed in U.S. Pat. Nos. 5,371,147, 5,314,960, and 5,057,578 incorporated in their entireties herein by reference, hydrogel, or silicone-containing hydrogel. More preferably, the surface is a siloxane, or contains a siloxane functionality, including, without limitation, polydimethyl siloxane macromers, methacryloxypropyl polyalkyl siloxanes, and mixtures thereof, silicone hydrogel or a hydrogel, such as etafilcon.
If the surface material to be coated does not contain the requisite hydroxyl or amine groups, such groups may be incorporated into the surface material. For example, hydroxyl groups may be incorporated by addition of one or more hydroxyl-containing monomers into the polymers used to form the surface. Examples of such hydroxyl containing monomers include, without limitation, mono(meth)acrylates of ethylene glycol, propylene glycol, glycerol, tetraethylene glycol, and the like. Amino groups may be incorporated using, without limitation, (meth)acrylates of aminoalcohols such as aminoethanol, tert-butylaminoethanol, or (meth)acrylamides of diamines such as bisaminopropane.
Alternatively, amine or hydroxyl functional, silicone-containing monomers or macromers may be used to incorporate the hydroxyl or amino functionalities into the surface. Suitable hydroxyl containing macromers include, without limitation, silicone containing linear or branched hydroxyalkylamine functional monomers of the structure: 
wherein: n is 0 to 500, m is 0 to 500, and n+m=10 to 500, preferably 20 to 250; R2, R4, R5, R6, and R7 are each independently a substituted or, preferably, unsubstituted monovalent alkyl of 1 to 10 carbon atoms or a substituted or, preferably, unsubstituted aryl group, suitable substituents for which include alcohol, ester, amine, ketone, carboxylic acid, or ether groups; R1, R3, and R8 are each independently a substituted or, preferably unsubstituted monovalent alkyl of 1 to 30 carbon atoms or a substituted or, preferably, unsubstituted aryl group suitable substituents for which are alcohol, ester, amine, ketone, carboxylic acid, or ether groups, and at least one of R1, R3, and R8 is of the formula: 
wherein R9 is any group capable of linking N to Si, including without limitation, a linear or branched divalent alkyl of 1 to about 10 carbon atoms or an ether group, R10 and R11 are each independently H, a substituted or unsubstituted monovalent alkyl of 1 to 5 carbon atoms, a substituted or unsubstituted aryl group, suitable substituents for which are substituted with alcohol, ester, amine, ketone, carboxylic acid, or ether groups, or the structure: 
wherein R14 is H or a monovalent (meth)acryloyl, styryl, vinyl, allyl, or N-vinyl lactam polymerizable group and preferably H or methacryloyl; R16 is H, a monovalent substituted or unsubstituted alkyl group of 1 to 6 carbon atoms, a substituted or unsubstituted aryl group, suitable substituents for which are alcohol, ester, amine, ketone, carboxylic acid, or ether groups, or a (meth)acrylate, styryl, vinyl, allyl, or N-vinyl lactam polymerizable group and preferably is an alkyl group of 1 to 6 carbon atoms substituted with an alcohol or is a methacrylate; R12, R13, and R15 are independently H, a substituted or unsubstituted monovalent alkyl of 1 to 6 carbon atoms, a substituted or unsubstituted aryl, suitable substituents for which include alcohol, ester, amine, ketone, carboxylic acid, or ether groups, or R12 and R15 or R13 and R15 form a ring structure with the proviso that at least some of the structure II groups on the monomer are polymerizable groups. Preferably, R12, R13, and R15 are H.
Silicone-containing polymers useful in the present invention may also be copolymers incorporating one or more hydrophilic monomers. The hydrophilic monomers used to make the hydrogel used in the invention may be any of the known monomers useful for hydrogel formation.
Preferred hydrophilic monomers used in forming the carboxyl functional hydrophilic containing surfaces useful in the process of this invention are acrylic or vinylic-containing. Acrylic-containing monomers contain the group (CH2xe2x95x90CRCOX) wherein R is H or CH3, and X is O or N. Examples of such monomers include, without limitation, N,N-dimethylacrylamide, 2-hydroxyethyl methacrylate, glycerol methacrylate, 2-hydroxy ethyl methacrylamide, polyethylene glycol monomethacrylate, methacrylic acid, acrylic acid, and the like.
Vinylic-containing monomers refers to monomers containing the group (xe2x80x94CHxe2x95x90CH2). Examples of such monomers include, without limitation, N-vinyl lactams, such as N-vinyl pyrrolidone, and N-vinyl-N-methyl acetamide, N-vinyl-N-ethyl acetamide, N-vinyl-N-ethyl formamide, N-vinyl formamide and the like. Preferably, the monomer is N-vinyl pyrrolidone.
Other hydrophilic monomers that may be employed in forming the surfaces of the invention include, without limitation, polyoxyethylene polyols having one or more terminal hydroxyl groups replaced with a functional group containing a polymerizable double bond. Examples include, without limitation, polyethylene glycol, ethoxylated alkyl glucoside, and ethoxylated bisphenol A reacted with one or more equivalents of an end-capping group such as isocyanatoethyl metliacrylate, methacrylic anhydride, methacryloyl chloride, vinylbenzoyl chloride, or the like to produce a polyethylene polyol having one or more terminal, polymerizable, olefinic groups bonded to the polyethylene polyol through linking moieties such as carbamate or ester groups.
Additional exemplary hydrophilic monomers are disclosed in U.S. Pat. Nos. 5,070,215 and 4,910,277, which are incorporated herein in their entireties by reference. Preferred hydrophilic monomers are N,N-dimethylacrylamide, 2-hydroxyethyl methacrylate, glycerol methacrylate, 2-hydroxyethyl methacrylamide, N-vinyl pyrrolidone, polyethylene glycol monomethacrylate, and (meth)acrylic acid. Most preferably, N,N-dimethylacrylamide is used.
The surface to be coated with the carboxyl functional hydrophilic polymer is contacted with the polymer and at least one coupling, agent in any convenient manner. For example, the device may be placed in a solution of polymer and solvent into which the coupling agent is added. As an alternative, and preferably, the device surface may first be contacted with one of the coupling agent or polymer and then contacted with the other. Most preferably, the surface is first contacted by any convenient method with the coupling agent for a period of about 0.5 to about 60 minutes, preferably for about 1 to about 30 minutes. For example, the surface may be soaked in a coupling agent solution. Subsequently, the surface is contacted with the carboxyl functional hydrophilic polymer solution for a period of about 1 to about 1000 minutes, preferably about 5 to about 200 minutes.
Suitable solvents for use in the invention are those that are capable of solubilizing both the carboxyl-functional polymer and the coupling agent. Preferably, the coating process is carried out in a water or aqueous solution, which solution preferably contains buffers and salts. The carbodiimide 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (xe2x80x9cEDCxe2x80x9d) is effective in aqueous solutions and, thus, is a most preferred coupling agent.
The coupling agents may be used alone or in combination with agents capable of stabilizing any reactive intermediate formed. For example, EDC may be used with N-hydroxysuccinimide as a stabilizer. Additionally, it may be necessary to adjust the solution pH in order to optimize ester or amide linkage formation. Preferably, the pH is adjusted to from about 2.0 to about 8.0, more preferably from about 4.5 to about 5.0.
A coupling effective amount of the coupling agent is used which amount is sufficient to couple the polymer to the device surface. The precise amount of coupling agent used will depend on the surface""s chemistry as well as the polymer and coupling agent selected. Generally, about 0.01 to about 10 weight percent, preferably about 0.01 to about 5.0, more preferably, about 0.01 to about 1 weight percent of the coating solution is used. By coating solution is meant the polymer with one or more of the solvent, coupling agent, and buffer. Typically, the amount of coating solution used per lens will be about 0.1 to about 100 g, preferably about 0.5 to about 50 grams, more preferably about 1 to about 10 g per lens.
A coating effective amount of carboxyl functional hydrophilic polymer is used meaning an amount sufficient to coat the surface to the desired degree. Generally, the amount of polymer used is about 0.001 to about 100, preferably about 0.01 to about 50, more preferably, about 0.01 to about 10 weight percent of the coating solution.
Temperature and pressure are not critical to the process, which may be conveniently carried out at room temperature and pressure. However, in a preferred embodiment, a temperature of about 30 to about 80xc2x0 C. is used. The contact time used will be a length of time sufficient to coat the surface to the extent desired. If the surface is being contacted with a coupling agent-polymer solution, generally, contact times will be from about 1 minute to about 24 hours, preferably from about 1 to about 120 minutes, more preferably from about 1 minute to about 60 minutes.
If the surface is first treated with only the coupling agent, the contacting time will be about 1 to about 120, preferably 2 to about 60 minutes. The surface then is contacted with the polymer-solvent solution as described above.
One ordinarily skilled in the art will recognize that the formulation for producing the surface to be coated by the method of the invention may contain other monomers and additives. For example, ultra-violet absorbing monomers, reactive tints, processing aids, and the like may be used.
Following contacting, the surface may be washed with water or buffered saline solution to remove unreacted polymer, coupling agent, solvent, and byproducts. Optionally, the coated surface may be heated in water to extract residual coating, coupling agent, and byproducts and to ensure the break down of any coupling agentxe2x80x94stabilizer complexes that may have formed.
The invention will be further clarified by a consideration of the following, non-limiting examples.